The present invention relates to the general field of transformers. In particular, the invention relates to a three-phase-two-phase stationary transformer with forced linked flux.
In certain situations, it may be necessary to transfer energy in balanced manner from a three-phase source to a two-phase source. Three-phase-two-phase stationary transformers are known, and in particular one that is said to be “Scott-connected”, and another that is said to be “Leblanc-connected”.
A Scott-connected transformer makes use of two single-phase transformers. The first has its n1 turn primary connected between terminals A and B of the three-phase network. The primary of the second transformer has n1′ turns and it is mounted between terminal C of the three-phase network and the midpoint M of the primary of the first transformer. The two secondary phases both have the same number n2 of turns. The primary voltages are in quadrature, and the same thus applies for the secondary voltages. To ensure that the secondary voltages have the same value and are in quadrature, it is necessary for:n1′=√3n1/2
The Scott connection presents several drawbacks. The magnetic circuits of the two single-phase transformers present considerable weight and bulk. Furthermore, the windings of the two transformers need to be different on the three-phase side since they do not have the same numbers of turns. Since the numbers of turns for the three-phase phases are different, the sections of the electrical conductors need to be different in order to guarantee balanced resistances for each of the phases. A star connection is required and it is therefore not possible to act on the voltage ratios with a delta connection or a zigzag connection. Finally, no advantage can be taken of the positive coupling of phases in a three-phase transformer with forced linked flux, which coupling makes it possible to reduce the magnetizing current needed.
The Leblanc connection uses a magnetic circuit with three, four, or five columns. In a three-column magnetic circuit, the transformer is a forced linked flux transformer, thus making it possible to limit the magnetizing current.
The Leblanc connection also presents drawbacks. The windings of the phases on the two-phase side need to be different since they do not have the same numbers of turns. The windings on the two-phase side are distributed on the three columns in non-symmetrical manner, thereby giving rise to different leakage inductances. Since the numbers of turns in each of the phases on the two-phase side are different, it is necessary to use electrical conductors of different sections in order to balance the resistances of each of the phases.
There thus likewise exists a need for an improved solution enabling energy to be transferred in balanced manner from a three-phase source to a two-phase source.